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Notice: This material is excerpted from Special Edition Using Java, ISBN: 0-7897-0604-0. The electronic version of this material has not been through the final proof reading stage that the book goes through before being published in printed form. Some errors may exist here that are corrected before the book is published. This material is provided "as is" without any warranty of any kind.

Appendix C- Java Language Grammar

A language grammar (sometimes called a statement of syntax), like the one contained in this appendix, is intended as an aid to understanding. You shouldn't try to use it in isolation, as it doesn't contain an exact statement of the language. In particular, you could write Java code that conforms to the "letter of the law" as stated in the grammar, but that doesn't follow the rules laid out elsewhere in the book, and you would end up with code that doesn't compile and won't run.

For example, the grammar for statements and expressions is carefully laid out in this appendix. But from chapters 9 and 13, you know that Java doesn't allow arbitrary combinations of data types. A statement or expression that conforms only to this grammar but that doesn't follow the type rules won't compile successfully. 

See "Operators" Chapter 8
See "Expressions in Depth" Chapter 12

As another example, this grammar describes legal forms for the declaration and use of variables. But Java imposes additional rules on variables that aren't covered in a grammar. The compiler goes to some lengths, for example, to make sure that variables are initialized before they are used; if the compiler thinks you are trying to use an uninitialized variable, it will give you an error. Those sorts of rules are not covered in the grammar of the language.

The formal specification for the Java language, including the grammar, is available online from JavaSoft. The main documentation page is located at http://java.sun.com/doc.html . Documentation specific to the JDK is available at http://java.sun.com/JDK-1.0/index.html The following grammatical elements refer to the corresponding character from the ASCII character set:

The following elements are as defined in the Unicode standard:

The subscript opt indicates that the element is optional; the element being defined will be legal (according to the grammar) with or without the optional element present.

Lexical Structure

Unicode Escapes and Character Input

EscapedInputCharacter:

UnicodeEscape:

UnicodeMarker:

RawInputCharacter:

HexDigit: one of

Input Lines

LineTerminator:

InputCharacter:

Tokens

Input:

InputElements:

InputElement:

WhiteSpace:

Token:

Comments

Comment:

TraditionalComment:

DocComment:

InputCharacters:

Keywords

Keyword: one of

Identifiers

Identifier:

Literals

Literal:

IntegerLiteral:

IntegerTypeSuffix: one of

DecimalLiteral:

Digits:

Digit: one of

NonZeroDigit: one of

HexLiteral:

OctalDigit: one of

FloatingPointLiteral:

ExponentPart:

ExponentIndicator: one of

SignedInteger:

Sign: one of

FloatTypeSuffix: one of

BooleanLiteral: one of

CharacterLiteral:

SingleCharacter:

Escape: one of

OctalEscape:

ZeroToThree: one of

StringLiteral:

StringCharacters:

StringCharacter:

Separators

Separator: one of

Operators

Operator: one of

Types and Variables

Type:

PrimitiveType: one of

ClassType:

InterfaceType:

ArrayType:

Program Structure

CompilationUnit:

PackageStatement:

PackageName:

PackageNameComponent:

ImportStatement:

PackageImportStatement:

TypeImportStatement:

TypeImportOnDemandStatement:

TypeDeclarations:

TypeDeclaration:

Classes and Interfaces

ClassDeclaration:

ClassModifiers:

ClassModifier: one of

Super:

Interfaces:

ClassBody:

Field Declarations

FieldDeclarations:

FieldDeclaration:

Variable Declarations

FieldVariableDeclaration:

VariableModifiers:

VariableModifier: one of

VariableDeclarators:

VariableDeclarator:

DeclaratorName:

VariableInitializer:

ArrayInitializers:

Method Declarations

MethodDeclaration:

MethodModifiers:

MethodModifier: one of

ResultType:

MethodDeclarator:

ParameterList:

Parameter:

Throws:

TypeNameList:

MethodBody:

Constructor Method Declarations

ConstructorDeclaration:

ConstructorDeclarator:

ConstructorModifier: one of

ConstructorBody:

ExplicitConstructorCallStatement:

Static Initialization

StaticInitializer:

Interface Declarations

InterfaceDeclaration:

InterfaceModifiers:

InterfaceModifier: one of

ExtendsInterfaces:

InterfaceBody:

Arrays

ArrayInitializer:

ElementInitializers:

Element:

Blocks and Statements

Block:

LocalVarDeclarationsAndStatements:

LocalVarDeclarationOrStatement:

LocalVariableDeclarationStatement:

Statement:

EmptyStatement:

LabeledStatement:

ExpressionStatement:

SelectionStatement:

IterationStatement:

ForInit:

ForIncr:

ExpressionStatements:

JumpStatement:

GuardingStatement:

Catches:

Catch:

Finally:

Expressions

Primary Expressions

PrimaryExpression:

NotJustName:

ComplexPrimary:

Name:

QualifiedName:

Array and Field Access

ArrayAccess:

FieldAccess:

Method Calls

MethodCall:

MethodAccess:

ArgumentList:

Allocation Expressions

AllocationExpression:

TypeName:

TypeKeyword: one of

ArgumentList:

DimExprs:

DimExpr:

Dims:

Unary Operators

PostfixExpression:

PostIncrement:

PostDecrement:

UnaryExpression:

PreIncrement:

PreDecrement:

UnaryExpressionNotPlusMinus:

CastExpression:

Arithmetic Operators

MultiplicativeExpression:

AdditiveExpression:

Shift Operators

ShiftExpression:

Relational and Equality Operators

RelationalExpression:

EqualityExpression:

Bitwise and Logical Operators

AndExpression:

ExclusiveOrExpression:

InclusiveOrExpression:

Conditional Operators

ConditionalAndExpression:

ConditionalOrExpression:

ConditionalExpression:

Assignments

AssignmentExpression:

Assignment:

AssignmentOperator: one of

Expression:

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